<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>UI元素状态伪类选择器</title>
		<style type="text/css">
			input:focus{
				color: blue;
			}
			input:required{
				border: 3px solid gray;
			}
			input:disabled{
				background: red;
			}
			textarea:read-only{
				color: red;
			}
			input:checked{
				width: 20px;
				height: 20px;
			}
		</style>
	</head>
	<body>
		<input type="text" placeholder="请输入内容" required="required"/><br />
		<input type="text" placeholder="禁用状态" disabled="disabled"/><br />
		<textarea readonly="readonly">只读状态</textarea><br />
		请选择城市：<input type="radio" value="" checked="checked" />北京
					<input type="radio" value="" />上海
	</body>
</html>
